Lurching engine on 86 Trooper HELP

On a 1986 trooper I go out and drive it and I'm still working out bugs from the engine rebuild. Me and a friend went and test drove it and it was fine until the engine warmed up and then it lurched and coughed like crazy and died altogether in the middle of the road. So we let it sit for a bit and try it again and its fine...for another 5 mintues. We get it home and he says its a crappy fuel pump. So I replace it and that helps alot but it still lurches periodicly after its warmed up but not so much. Could it be a bad O2 sensor? Help would be appreciated. Kevin